“Aircraft” may be any type of manned aircraft and unmanned aircraft, such as so-called unmanned air vehicles or unmanned combat vehicles being autonomous but possibly also partially controllable from the ground. In the case of a manned aircraft it may be a civilian aircraft, but the invention is particularly directed to military aircraft, so that particular application will hereinafter be described for illuminating the invention but accordingly not restricting the scope thereof.
All aircraft, civilian as well as military, have a transponder continuously broadcasting data associated with the position, the velocity and the identity of the aircraft and receiving corresponding data from other aircraft. Accordingly, said transmitter and receiver are then present in the form of such a transponder.
The aircraft have also a so-called de-conflicting system for avoiding mid-air collisions, i.e. collisions between two or more aircraft. The most common such system is the TCAS system (traffic collision avoiding system). This system involves a processing of said transponder data for calculating through the on board computer of the aircraft whether there is a risk that the predicted flight trajectory of the aircraft cross any predicted flight path of another aircraft. When it is determined that such a risk exists a warning means delivers an alert for avoiding a later collision. This means in the case of a manned aircraft that the pilot in the respective aircraft may then without coming under time pressure change the flight path for avoiding a collision. This calculation is carried out by a simple tracking algorithm requiring comparatively limited computer capacity. In the case of an unmanned aircraft a modified flight path may automatically be selected upon such an alert indicating the risk of a later collision.
Known are also so-called automatic collision avoiding systems (ACAS) designed to be the last protection against mid-air collisions between two or more aircraft. Such systems are adapted to select an automatic so-called fly-out of the aircraft for avoiding a collision with another aircraft coming close thereto. For this sake the algorithm used to select an automatic fly-out path in a direction selected by maximising the distance between own and other aircraft automatic fly-outs requires a lot of computer capacity, so that it is not, at least at present, possible to have such a system switched on other than under very special circumstances.
The function of the means determining a risk of crossing of predicted flight paths and delivering an alert for avoiding a later collision is very important for safety reasons. However, this so-called de-conflicting system is in conflict with the purpose of air combat training sessions of aircraft, since this de-conflicting system will then continuously warn an aircraft, and when manned the pilot, of other approaching aircraft. This means that it is not possible to train the aircraft and/or pilot to handle difficult situations suddenly occurring as a surprise and requiring instantaneous actions. To the contrary, the pilot will well in advance always be aware of the position of threatening aircraft approaching.